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当前学科:柴油机的换气与增压
题目:
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气阀通常采用两根内外旋向相反的弹簧,其目的是()。
A . A.提高弹簧疲劳强度
B . B.避免弹簧发生共振
C . C.防止弹簧断裂时气阀落入气缸
D . D.上述三点都是
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